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Long term low thyroid hormone is also an instigator of infertility.
The body will act to stabilize the thyroid hormone imbalance by releasing additional TRH (thyroid-releasing hormone) to stimulate the release of TSH (thyroid-stimulating hormone). Encouraging further TRH will also increase prolactin production which negatively impacts ovulation.
Also, your bodies own response to long term low thyroid hormone is to rely on cortisol (adrenal hormone). Prolonged cortisol elevations will decrease the liver’s ability to clear excess estrogens from the blood, which then increase the levels of thyroid TBG (transport proteins that thyroid hormone is attached to). When thyroid hormone is bound to TBG, it is inactive as must be cleaved from TBG to become “free-fraction” and activate cellular receptors, so making the problem worse... (shown in lab tests as “free T4 [FT4]” and “free T3 [FT3]”.
Levothyroxine takes up to 6 weeks to initially saturate the body which will only tolerate small increases at any one time. The goal of Levothyroxine is to restore the patient to euthyroid status and for most people that means TSH just above or below 1.0 but your doctor should retest your thyroid hormone levels after 6 weeks and adjust the dose according to results, knowing you are hoping to conceive.
Leave 24 hours between last dose and blood draw and have the blood drawn early in the morning whilst fasting (water only) as this is when TSH is highest.
It is important to take your pill on an empty stomach with a glass of water, 1 hour before food, 2 hours before supplements and 4 hours before calcium, iron or vit D supplements. People with thyroid issues often have vitamin deficiencies so ask your doctor to test Vit B12, vit D, folate and ferritin as optimum levels are required to ensure thyroid meds are used properly.
If you post any future blood test results complete with ranges ( numbers in brackets) members will comment. Symptoms can often last many months, even after good biochemistry results.
NICE advise to delay conception until stabilised on levothyroxine (LT4) treatment. If your doctor is awkward, ask for an endo referral.
Good luck ...
Adrenal & Thyroid Connection
Infertility and Miscarriage in Subclinical Hypothyroidism.